US3315847A - Plunger - Google Patents

Description

April 25, 1967 Filed May 13, 1965 D. E. TRUMBULL PLUNGER 2 Sheets-Sheet 1 INVENTOR DONALD E. TRUMBULL ATTORNEYS April 25, 1 D. E. TUMBULL PLUNGER 2 Sheets-Sheet 2 Filed May 13, 1965 FlG .6

Fl G 5 INVENTOR. DONALD E. TRUMBULL ATTORNEYS United States Patent 3,315,847 PLUNGER Donald E. Trumbull, Birmingham, Mich, assignor to Pyles Industries, Inc., Southfield, Mich., a corporation of Michigan Filed May 13, 1965, Ser. No. 455,419 1 Claim. (Cl. 222-327) This invention relates to improvements in plungers used to dispense material from a cylindrical cartridge such as is commonly provided for sealant guns and the like.

Sealant guns of the general type shown in US. Patent No. 3,042,268 include a rigid barrel releasably coupled at its rearward open end to a cap assembly. Disposed within the barrel is a replaceable cartridge dispenser comprising a generally cylindrical plastic cartridge containing sealant compound and having a nozzle projecting through the barrel forward end, with a plunger in the cartridge behind the sealant compound whereby the sealant is dispensed through the cartrdige nozzle upon shiftable movement of the plunger Within the cartridge. Fluid under pressure is admitted to the rear end of the cartridge via valve means in the cap to urge the plunger against the sealant compound to dispense the compound through the nozzle.

Various modifications have been made in these sealant guns, and particularly the dispenser comprising the plunger and plastic cartridge, as shown for example in US. Patent No. 3,066,836. The instant invention relates specifically to an improved plunger for use in a plastic cartridge of slightly different configuration than is disclosed in the above patents. While various changes have been made in the barrel to accommodate the new cartridge, this application is concerned only with the provision of an improved plunger, and therefore the remaining parts of the sealant gun are described only to provide a setting for the plunger.

An object of the invention is to provide a plunger for use with a plastic cartridge containing sealant compound to dispense compound from the cartridge upon application of force to the plunger, as by the pressure of air thereagainst, said plunger being so constructed as to obviate any possibility of the plunger tipping within the cartridge while being of an axial length relative to its diameter so that it does not take up an inordinate amount of space within the cartridge.

Another object is the provision of a plunger of the character described having a relatively sharp peripheral forward edge cooperable with the inner cylindrical cartridge wall to wipe sealant compound therefrom as the plunger is urged forwardly against the compound. A concomitant object is the provision of a plunger having a configuration such that the plunger may seat against the forward wall of the cartridge to expel substantially all of the sealant compound from the cartridge when the plunger is shifted all the way forward in the cartridge.

Another object is the provision of such a plunger having a forward wall having a surface area greater than the cross-sectional area of the cartridge and of such configuration that upon the application of pressure fluid against the plunger said wall will transmit the force to the leading peripheral edge of the plunger urging such edge into intimate contact with the cartridge inner wall.

A further object is the provision of a plunger having a forward wall of the character above set forth, a portion of which wall is deformable to permit limited displacement of the wall forwardly upon the application of force thereagainst, whereby upon the removal of force against the wall the latter will return to its original position to increase the effective volume of the cartridge forwardly of the plunger, that is, the portion containing the sealant compound, and thus to prevent continued discharge of 3,3 15,847 Patented Apr. 25, 1967 compound from the nozzle when rupted.

Another object is to provide a plunger of the character above set forth, wherein the forward wall of the plunger is provided with an aperture through. which the material to be dispensed may be introduced into the cartridge, beginning with the plunger disposed at the extreme forward end of the cartridge, and the plunger cont-acting the material and being shifted toward the rear end of the cartridge as the latter is filled with material, obviating the entrapment of air within the cartridge adjacent the plunger as may occur when the cartridge is first filled and the plunger is thereafter inserted. A concomitant object is the provision of such a plunger together with a novel plug which is adapted to be sealingly engaged within the plunger aperture while the plunger is positioned in the cartridge after the latter has been filled with material.

Other objects, advantages and meritorious features will more fully appear from the following specification, claims and accompanying drawings, wherein:

FIG. 1 is a longitudinal view partly in section of a sealant gun of the general type hereinab-ove defined, showing a plunger embodying the invention disposed within a dispensing cartridge;

FIG. 2 is an enlarged partial longitudinal section showing the relationship of the plunger within the cartridge;

FIG. 3 is a front elevation of the plunger embodying the invention;

FIG. 4 is a partial section similar to FIG. 2 showing a modified plunger having an aperture in its forward wall and a plug sealingly engaged within the aperture;

FIG. 5 is an exploded view of the structure of FIG. 4 showing the plug removed from the plunger aperture;

FIG. 6 is a rear elevation of the plunger shown in FIGS. 4 and 5; and

FIG. 7 is a front elevation of the plug shown in FIGS. 4 and 5.

While the sealant gun 10 shown in FIG. 1 may exhibit various forms, for purposes of illustration it may comprise a rigid barrel 12 of cylindrical shape having a cartridge nozzle-receiving opening 14 at the forward end thereof and a compressible gasket 16 of sponge rubber or the like encircling the opening 14. A replaceable polyethylene cartridge 18 is disposed within the barrel 12 and has an integral nozzle 20 which projects through the opening 14, while the front face 21 of the cylindrical cartridge portion bears against the gasket 16. A. valve closure cap 22 is coupled to the open rear end of the barrel 12 by a releasable retainer assembly indicated generally at 24. A valve actuating lever 26 is pivotally mounted on cap 22 for controlling the admission of fluid under pressure to the open rear end of the cartridge 18.

Slidably disposed within the cartridge 18 is a material dispensing plunger 28 against which fluid pressure admitted through cap 22 acts to urge the plunger forwardly toward the nozzle 20 and press againt the sealant compound in the cartridge, dispensing the compound through the nozzle. The integral cartridge nozzle 20 is manufactured with the tip thereof sealed, and when it is desired to dispense sealant compound from the cartridge 18, the nozzle tip is cut oif as shown at 30. As the nozzle 20 is tapered, it may be cut off at any point along its tapered length to provide a nozzle opening of correct cross-sectional area for the particular application.

The plunger 28 is slidably received within the cylindrical cartridge 18 and comprises a forward Wall 32 extending generally transversely of the cartridge and a rearwardly extending skirt 34 of substantially cylindrical configuration. The plunger is positioned in the cartridge as shown in FIGS. 1 and 2 to be shifted from left to right therein. The forward wall 32 of the plunger 28 includes dispensing is intercircular, disk-like central portion 36 and an annular onnecting portion 38 integrally joining the periphery of he disk 36 to the extreme forward or leading edge 40 vf the skirt 34. As shown, the wall portion 36 extends terpendicularly to the longitudinal axis of the cartridge [11d plunger, which are of course co-axially arranged, and s also spaced rearwardly from the leading edge 40 of the .kirt 34. Wall portion 38 extends radially and forwardly ?rom the periphery of disk 36 to the leading edge 40 of he skirt 34, and defines an acute interior angle with the tkirt.

The plunger is preferably constructed of plastic such as olyethylene or the like. As shown most clearly in FIG. 2, the central disk portion 36 of forward wall 32 is relaively thick in comparison to the remaining portions of the plunger 28, and by reference to FIG. 3 it can be seen that the disk 36 is reinforced by a series of radially ex- :ending spokes or ribs 42 and a peripheral reinforcing rib 44 to impart rigidity to the disk. The wall portion 38 on the other hand is thinner than the disk 36 and is intended to be somewhat flexible or deformable, and in fact the portion 38 is intended to act somewhat like a diaphragm upon the application of fluid under pressure to the plunger, as more fully described hereinafter.

The cylindrical skirt 34 of the plunger 28 is slightly outwardly flared as shown in FIG. 2 at 46, and such skirt portion is also flexible. The diameter of the trailing edge 48 of skirt 34 is very slightly greater than the inner diameter of the cylindrical cartridge 18, so that upon insertion of the plunger within the cartridge the rear portion of the skirt 34 deforms slightly radially inwardly to insure intimate contact of the edge 48 against the inner wall of the cartridge 18.

Upon the introduction of air or other fluid under pressure to the open rear end of cartridge 18 through valve cap 22, the skirt 34 of piston 28 is urged by the pressure of the incoming fluid into circumferential sealing engagement against the interior wall of the cartridge. With the trailing edge 48 of skirt 34 slightly oversize the cartridge, as noted above, the skirt trailing edge is already in intimate engagement against the cartridge wall before pressure is applied, and there is thus no tendency for the air to seep between the plunger skirt and the cartridge wall. Hence the air under pressure acts against the skirt to urge the trailing edge thereof into positive sealing engagement with the cartridge.

As stated above, the central disk portion 36 of the forward plunger wall 32 is rigid, while the annular portion 38 is comparatively flexible. Thus when air under pressure is directed against the rearwardly facing surface of wall 32, the rigid disk portion 36 tends to shift sightly forwardly with respect to skirt 34, thus exerting a force on annular portion 38. Because of the particular disposition of portion 38 with respect to portion 36 and skirt 34, a component of force is directed generally radially outwardly against the leading edge 40 of skirt 34, urging such edge into sealing contact with the inner wall of cartridge 18, thereby scraping the sealant compound from the cartridge wall as the plunger is shifted forward toward nozzle 20. The edge 40 is relatively sharp so that the wiping contact thereof against the cartridge wall will effectively clean the cartridge of sealant compound.

As the sealant compounds are usually fairly viscous, there is an appreciable resistance to forward movement of the plunger in the cartridge acting against the forwardly facing surface of plunger wall 32. Because of the particular disposition of the wall portion 38, however, the force acting thereagainst does not adversely affect the seal of the edge 40 against the cartridge but rather aids it, as there is a component of such force acting radially outwardly, i.e., in a direction tending to urge the edge 40 into engagement with the cartridge wall.

One of the problems encountered in providing a satisfactory dispenser for sealant guns, more particularly sealant guns Which utilize air under pressure to shift the dispensing plunger, has been to provide a plunger which will not tip or become cooked in the cartridge when air pressure is applied thereagainst. If this does occur, it is obvious that the air by-passes the plunger, rendering the dispenser useless. The plunger herein described, in addition to its other attributes, is virtually impossible to tip. It has been found that even if the initial inrush of air against the plunger wall 32 is not uniformly distributed thereacross, the unique configuration of the wall prevents any misalignment of the plunger in the cartridge.

In FIGS. 4-7 inclusive there is shown a modified plunger generally indicated at 28'. Such plunger is identical in many respects to the plunger 28 of FIGS. 1-3, and the same reference numerals have been used to identify identical structure. The difference between the plungers 28 and 28 lies in the construction of the central portion of the forward wall 32 of the latter, shown at 50 in FIGS. 4-7.

The wall portion 50 differs from that previously described in the provision of an axial aperture 52 opening therethrough, within which is positioned a removable plug 54. The advantage of this construction will become apparent as the description proceeds. Aperture 52 tapers inwardly toward the forward plunger surface, and is of truncated conical shape. Plug 54 comprises a forward tapering portion 56, an intermediate tapering portion 58, and a cylindrical rear portion 60. The forward and intermediate tapering portions 56 and 58 define therebetween a radially extending circumferential shoulder 62, while the rear portion 60 projects beyond portion 58 to define a second similar shoulder 64. The dimensions of intermediate portion 58 of plug 54 are substantially identical to the size of the opening in the plunger defined by the walls of aperture 52.

As can be seen most clearly in FIG. 6, the rearwardly facing surface of forward wall 50 exhibits a plurality of radially extending reinforcing ribs 66 similar to the ribs 42 on plunger 28, and provided for the same purpose. The plug 54 is made out of a suitable plastic material such as polyethylene, preferably the same material as the plunger 28'.

Referring briefly to FIG. 1, the cartridge 18 is provided with a transverse forward wall 21 and the integral nozzle 20 projects axially from such forward wall. As heretofore stated, the nozzle 20 is sealed at its forward end during manufacture, and the nozzle tip is cut off as shown at 30 in FIG. 1 for dispensing. In filling the cartridge 18 utilizing the plunger 28 of FIGS. 4-7, the nozzle 20 is still sealed, and the filling operation is commenced with the plunger in the cartridge 18 positioned with its forward edge 40 in engagement with cartridge wall 21, as shown at 28 in FIG. 1. Material is then introduced into the cartridge through the aperture 52 in plunger 28, and as the cartridge forwardly of the plunger is filled with material, the pressure of incoming material acts against the forward face 32' of the plunger to shift the latter rearwardly in the cartridge until the cartridge has been charged with the proper amount of material. The forwardly facing surface of wall 32 of plunger 28' is then in intimate contact with the material in the cartridge, and the possibility of air being entrapped between the plunger and the charge of material is virtually eliminated, because the air may easily escape through aperture 52.

Once the cartridge 18 has been filled with material, with the plunger 28 in intimate contact therewith, the plug 54 is inserted into aperture 52. The plug 54 is sufliciently resilient so that its forward portion 56 will deform slightly as it is urged through aperture 52, and thereafter return to its normal shape whereby shoulder 62 will engage the front surface of the plunger wall portion 50, while shoulder 64 will be urged into contact with the rear surface of wall portion 50. Thus the opposite marginal edges of aperture 52 are circumferentially sealingly engaged by the shoulder portions 62 and 64 of the plug 54 when the plug is engaged in the plunger. As the shape of plug portion 56 conforms to the shape of aperture 52, the surface of the plug intimately contacts the aperture Wall during insertion of the plug, and there is thus no opportunity for material in the cartridge to escape between the plug and the plunger during insertion of the plug. Upon assembly the structure is as shown in FIG. 4.

The operation of the plunger 28 during dispensing of material from the cartridge 13 is exactly the same as described hereinabove with respect to plunger 28. The slight shifting movement of forward wall 32' upon the application of air under pressure to urge the plunger 28' forwardly in the cartridge is insufficient to aflFect the seal between the plunger aperture 52 and the plug 54.

What is claimed is:

A material dispensing plunger for use in a cylindrical cartridge having an open rear end and a nozzle opening at the forward end thereof comprising a generally cup-shaped plunger member slidably receivable within said cartridge having a forward Wall and a cylindrical skirt extending rearwardly from said forward wall terminating in a free trailing edge having a diameter slightly oversize the cartridge inner diameter for intimate contact with the cartridge Wall, said forward Wall comprising a relatively rigid non-deformable central portion having an aperture of truncated conical shape opening therethrough and a relatively flexible peripheral portion integrally connecting the central portion to the leading edge of said plunger skirt with said central portion spaced rearwardly of the skirt leading edge and said peripheral portion being planar and extending radially and forwardly from said central portion to and intersecting said skirt leading edge at an acute angle to provide a relatively sharp circumferential edge in sliding engagement with the inner cartridge wall, and a solid resilient plug for engagement within said central portion aperture, said plug having a tapering nose portion, a truncated conical intermediate portion corresponding in shape to the plunger aperture and a rear end portion, and a pair of radially projecting shoulders on said plug at opposite ends of the intermediate portion adapted to sealingly overlie the opposite marginal edges of said aperture upon engagement of the plug within the plunger.

References Cited by the Examiner UNITED STATES PATENTS 1,447,030 2/1923 Miller 222563 X 2,923,442 2/ 1960 Maras 222-327 2,925,941 2/ 1960 Bloxom 222261 3,022,923 2/ 1962 Hoffman 222389 X 3,042,268 7/1962 Pyles 222-3 89 X 3,066,836 12/1962 Trumbull 222-389 X 3,075,675 1/1963 Wormser et al 222--327 3,250,443 5/1966 Abbott 222327 ROBERT E. REEVES, Primary Examiner. WALTER SOBIN, Examiner.

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